Process for producing inks



Dec. 27, 1966 R. E. DOBBIN ETAL PROCESS FOR PRODUCING INKS OriginalFiled Dec. 27, 1961 United States Patent 3,294,567 PROQESS FUR PRODUCINGINKS Roiiins E. Dobbin and Curt B. Beck, Pampa, Tex., assignors to CabotCorporation, Boston, Mass, a corporation of Delaware Continuation ofapplication Ser. No. 162,423, Dec. 27, 1961. This application Jan. 18,1965, Ser. No. 426,314 5 Claims. (Cl. 106-34) This application is acontinuation of application Serial Number 162,423 filed December 27,1961 and now abanboned.

This invention relates to inks. More particularly, the inventiondisclosed herein relates to a process for producing improved newsinks.

It would normally be expected that an old and established art such asink making would by now be developed to a point approximatingperfection. Nevertheless, serious problems often still persist inproduction of commercially acceptable inks when certain pigments areutilized. In fact, one of the chief problems in ink making today hasalmost continually plagued the industry since its inception; i.e. theproblem of conveniently and economically obtaining an ink meeting theindustrys residue specifications. Due to the requirement for lowresidue, the ink maker has only recently been able to escape theinconvenience attendant the use of the dusty, fluffy form of carbonblack which was resorted to in order to obtain the low residue desiredwith inexpensive milling equipment. The use of carbon black in fluffyform, aside from the obvious undesirable aspects implicit in itshandling, also presented additional costs to the industry since specialbagging and uneconomical methods of shipment were required to deliversame. A remedy to the necessity for using the flutfy form of carbonblack appeared to have been effected when the carbon black industrydeveloped means of :agglomerating the carbon black into soft pelletswhich could apparently be satisfactorily dispersed in ink vehicles byordinary milling equipment. However, because of the many minoruncontrollable variables inherent in the pelletization process, inkscomprising this special pelletized form of carbon black often failed tomeet all of the exacting specifications of the ink industry especiallywith regard to maxi-mum residue specifications. Accordingly, althoughpelletized carbon black solved most of the major problems posed by theuse of their fluffy counterparts nevertheless the inferior inksfrequently produced when said pelletized carbon blacks were utilizedstill left much to be desired.

In the newsink industry, the specifications asto maximum residueallowable are especially stringent. According to the levigation testnormally utilized in measuring residue, an acceptable ink is indicatedwhen the maximum residue left on a 325 mesh screen when carbon black isdispersed in an ink vehicle at a carbon black concentration of 10% bymeans of an Eppenbach-type mill is not over 0.03%. Accordingly, anyprocess which is readily adaptable to already existing commercialpractice and which would insure the production of inks whichconsistently meet and conform to the rigorous residue specificationsrequired by the newsink industry would be a notable and valuablecontribution to the art.

The principal object of the present invention is to provide a processwhich yields improved inks.

Another object of the present invention is to provide a process whichinsures the production of an ink which consistently conforms to thespecifications required by the ink industry.

Still another object of the present invention is to provide a simple,economical process for producing carbon black pellets particularlysuitable for use in ink, especially newsinks.

"ice

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

The above obpjects and advantages are realized in accordance with thepresent invention by utilizing in producing the ink, carbon blackpellets from which there has I been removed by screening out orotherwise, a certain fraction of the pellets representing those ofsmallest diameter. We have discovered that the pellets of smallestdiameter, which will hereinafter be referred to as the fines, appear tocontain all or at least substantially all of the offending factorsresponsible for the overall in ferior performance of the presentlyproduced inks. Accordingly, we have found that the removal orelimination of these fines and the subsequent use of the remainingpellets in the production of inks results in inks which normallyinvariably meet the residue specifications of the ink industry.

Generally the fines represent form about 5 to about 8% by weight of thetotal pellets of carbon black and usually correspond to those pelletshaving equivalent diameters of less than about microns. However, in someinstances where the pelletization process has been prolonged or carriedfurther, the fines which must be removed may include pellets havingdiameters up to about 280 microns. In such cases the fraction of finesremoved may be represented by as much as 10% or more by weight of thetotal pelletized carbon black and sometimes up to about 20%.Accordingly, the amount of fines removed in our process will generallyrepresent from about 5 to about 15% by weight of the total pellets butin some cases may amount to as much as 10 to 15 or even 20% by Weight ofthe total original pellets.

We are presently unable to explain precisely why the removal of thefines results in the production of a superior ink. According to ahypothesis which we have postulated but to which we do not wish to bebound, we believe that the percent mineral ash, especially iron grit, ispresent in considerably higher concentration in the fines than in otherpellet portions and might be the factor which is primarily responsiblefor the inconsistent and often inferior performance of the resultinginks where said fines are not removed. This hypothesis is consistentwith our present belief that the undesirable residue often found in inkscomprises a nucleus of small ash particles having built up thereonlarger particles of carbon black. For example, we have found that theresidue to an ink comprising a particular carbon "black is greatlydecreased when said black in fluffy form is first passed through aMikro-atomizer rather than the presently used Mikro-pulverizers.Mikro-pulverizers are hammer type mills produced by Pulverizing MachineCo., which are used in the carbon black industry to reduce in excess of99% of the black to a particle size of less than 44 microns.Mikro-atomizers such as those also produced by Pulverizing Machine Co.,are relatively new and have rotating elements consisting of hammers,classifier wheels and fans arranged in such a manner that carbon 'blackparticles may be recycled to the grinding zones until they are reducedto a uniform particle size of less than about 12 microns. Accordingly,the Mikro-atomizer treatment is believed to grind the ash particles tosuch a degree of fineness that they cannot further act as nuclei.Obviously, however, such a treatment especially of all of the carbonblack is expensive and inconvenient and accordingly undesirable from acommercial standpoint. Now, however, according to our discovery, suchtreatment of all the black is unnecessary.

As stated, the regular use of carbon black in pelletized form isrelatively new to the art of ink making. However, pelletized carbonblacks especially carbon blacks intended for use in newsink andprocesses for making same are now well known. (See for example, US.Patent 3,011,-

902.) Said pelletization processes essentially involve the mixing of anyof the wide variety of carbon blacks available for ink formulation witha definite proportion of oil, or emulsions of oil and water with orwithout surfactants. The mixture is then agitated in a suitablepelletizer under conditions sufficient to produce a soft, easilydispersible pellet. Generally today, the pellets are produced byuniformly distributing on the fluffy black about 2% to by weight of theblack of hot oil and subjecting the mixture to a tumbling type agitationfor about one hour. Although many of the present commercialpelletization processes theoretically should consistently producesatisfactory pellets, nevertheless, the inks produced therefrom oftenfail to meet residue specifications. Thus, our process insures theconsistent production of highly dispersible carbon black pellets and inturn commercially acceptable high quality ink, particularly newsink.

The particular oil utilized in producing the inks of the presentinvention is not critical. Thus, any oil which is normally utilized inproducing pellets for newsink use is generally entirely suitable for thepurposes of the present invention.

The practice of our invention will be better understood by reference tothe attached drawing, in which FIGURE 1 represents a flow sheetdescribing schematically an arrangement of apparatus satisfactory toproduce pellets of carbon black suitable for use in accordance with thepresent invention.

Referring now to the figure, carbon black is generally fed in fluffyform directly from the production unit (not shown) through aMikro-pulverizer 2 into an agitator tank 4. In the agitator tank 4, thetapped density of the black is increased to about 8 to 14 lbs/cu. ft.Thereafter the black is conveyed to a wet mixer 8. In the wet mixer aregulated amount of heated oil from reservoir 26 is usually sprayed ontothe black. The black and oil mixture is then conveyed to a dry drumpelletizer 12, wherein the black is pelletized to a density of about to18 lbs./ft. Alternatively, the fluffy black and hot oil may be mixeddirectly in the pelletizing drum 12 by means of a spray nozzlepositioned so that the oil impinges on the stream of fluffy black as itenters the pelletizing drum. In such a procedure, the pin type mixer 8would be eliminated. In any event, in order to produce pellets suitablefor use in our improved inks, the so produced pellets are thereafterconveyed from the pelletizer 12 to a screening or separating device 14,whereby the pellet fraction comprised of those pellets smaller than 150microns and preferably those smaller than 280microns are removedtherefrom. The remaining pellets which generally comprise from about 85to about 95% by weight of the total original pellets (depending upon thecut removed) are then conveyed to storage 18 and are ready for dispersalin an ink vehicle to produce the improved inks of the present invention.The fines, i.e. that portion of the pellets removed by device 14, maythen be discarded if desired. More preferably however, we have foundthat the fines can be conveyed to a grinding device such as aMikro-atomizer and after being pulverized therein, can be recycled toeither the dry pelletizer drum 12 or to the agitator tank 4 to producesatisfactory pellets.

In order to demonstrate more clearly the beneficial results obtained byour invention and to illustrate manners of practicing same, specificexamples are present below. These examples are illustrative in natureand in no way 1 are they to be construed so as to limit the scope of thepresent invention.

Example 1 A fluffy, high abrasion, oil furnace black produced by CabotCorporation was mixed with 6% mineral oil by weigh-t of the carbonblack. The mixing was accomplished by spraying a fine mist of the oil,which had been heated to about 250 F., onto the black as the fluffyblack entered a drum-type pelletizer. Subsequently, the mixture of blackand oil was pelletized in the pelletizer which rotated at a speed of 15rpm. at a black throughput of 30,000 lbs./ day. The pellets produced bythis method had a pour density of about 17-19 lbs/ft. and a WesternElectric crushing strength of from about 13 to 15 lbs. Three samples ofthe oil bound pellets produced as described above were dispersed to theextent of 10% of the pellets in a newsink oil by means of a colloid millof the Eppenbach QV-7 type. The percent 325 mesh ink residue of each ofthe inks was determined in conformity with the aforementioned standardlevigation test. The following data was obtained.

TABLE I Sample number: Percent 325 mesh ink residue 1 0.108 2 0.095 30.076

TABLE II Percent by Percent 325 Sample Number Weight of Mesh Ink TotalPellets Residue Removed From the above it may readily be seen thatremoval of the finer fraction of the pellets resulted in the productionof inks which are completely acceptable to the newsink industry.

Example 2 An ink made by dispersing 10% by weight of Sterling 99, an oilbound, fine furnace carbon black produced in pelleted form by CabotCorporation, in a newsink oil by a colloid mill of the Eppenbach QV-7type had a percent 325 mesh ink residue of 0.034. The pellets of acorresponding sample of Sterling 99 pellets were screened so as toremove that portion of said pellets having diameters less than aboutmicrons. The portion removed represented about 4% by weight of the totalpellets produced. An ink produced as described above from the remainingcoarser pellets has a percent 325 mesh ink residue of 0.027.

Substantially the same results as described above are obtained whenpellets produced by other processes are utilized. Thus, those carbonblacks pelletized by agitating a flocculent color black with anysuitable pelletizing oil known to the art including oil and wateremulsions, and emulsions which also comprise various surfactants can betreated in accordance with the present invention to yield superiorcarbon black pellets.

The inconsistencies between the percent 325 mesh ink residue of the inksof Table I (0.076-0.l08%) of Example 1 graphically illustrate theproblems which vex the ink producer. In turn those inconsistencies areusually attributed to the minor uncontrollable variations in the fuelsand waters utilized in the production of the carbon black and also tothe variables inherent in other operational features all of which renderdifficult precise control over the properties of the inks produced withthe resulting blacks. However, as the above examples illustrate, ourprocess is one which in one aspect-Example 1represents a method ofsatisfactorily compensating for these problems and in anotheraspectExample 2represents a method for adjusting and reducing theresidue of inks comprising carbon blacks which are produced within oronly slightly above the required specification.

Example 3 550 lbs. of a fluffy, high abrasion oil furnace carbon blackproduced by Cabot Corporation was pelletized in accordance with theprocedure described in Example 1. The resulting pellets were dispersedto the extent of of the pellets in a newsoil by means of a colloid millof the Eppenbach QV-7 type. The 325 mesh residue of the resulting inkwas 0.045%. Thereafter the pellets were screened so as to remove thatportion thereof which will pass through a 65 mesh screen. The pellets ofeach fraction (+65 mesh and 65 mesh) were dispersed in a newsink oil asdescribed above. The following data was The pellets representing the 65mesh fraction were thereafter reground in a Mikro-pulverizer and aftersuch treatment repelletized. The pellets produced after regrinding ofthe 65 mesh fraction were dispersed in a newsoil as described above andthe percent 325 mesh residue of the resulting ink was found to be0.010%.

The above example illustrates that not only does the process of thepresent invention produce inks having satisfactory residue levels butalso that such may be obtained without the sacrifice of any of theoriginal carbon black utilized and without involving any significantadditional expense. Accordingly, the preferred embodiment of ourinvention contemplates the separation of the fines from commercialpelletized carbon blacks and the sub-- sequent repulverization thereofto produce a product which may be recycled to the pelletization step toproduce pelletized carbon blacks entirely suitable for use in the inksof the present invention.

Since the essence of our invention resides essentially in the discoverythat inks produced with carbon blacks from which the finer pellets havebeen removed consistently have residues below 0.03%, there are manypossible modifications which can be made in the incidental features ofthe process. Accordingly, various methods of removing the finer portionof the carbon black pellets such as air elutriation, may be utilized andvarious pellet ized carbon blacks can be treated in accordance with theteachings of our process without departing from the spirit and scope ofour invention.

Also, it is obvious that the inks of the present invention can comprisein addition to carbon black and an oil vehicle, any other pigments and/or additives normally added to ink formulations.

Having described our invention, what we declare as new and desire tosecure by US. Letters Patent is as follows:

1. In a process for the production of carbon black pellets for use ininks which comprises agitating a flocculent color grade carbon black inthe presence of a pelletizing medium consisting of oil or oil/wateremulsions until said flocculent black has been substantially com pletelyconverted into discrete dustless pellets which are suitable for use ininks except for an undesirably elevated levigation factor theimprovement which comprises: depressing said levigation factor to anacceptable level by removing from the total mass of said pelletsessentially only those pellets having diameters of less than about 280microns and recovering the remaining pellets as finished product.

2. The process of claim 1 wherein the fine pellets removed representbetween about 5 and about 20 weight percent of the total pellets.

3. The process of claim 1 wherein the pellets removed are mechanicallypulverized and converted to the fluffy state and thereafterrepelletized.

4. In a process for the production of carbon black pellets for use ininks which comprises agitating a flocculent color grade carbon black inthe presence of a pelletizing medium consisting of oil or oil/wateremulsions until said flocculent black has been substantially completelyconverted into discrete dustless pellets which are suitable for use ininks except for an undesirably elevated levigation factor theimprovement which comprises: depressing said levigation factor to anacceptable level by removing from the total mass of said pelletsessentially only those pellets having diameters of less than aboutmicrons and recovering the remaining pellets as finished product.

5. The process of claim 4 wherein the fine pellets removed representbetween about 5 and about 15 weight percent of the total pellets.

References Cited by the Examiner UNITED STATES PATENTS 2,167,674 8/1939Offutt 106307 2,699,381 1/1955 King 106307 2,794,747 6/1957 Bloch 106282,891,872 6/1959 Voet 10628 2,942,299 6/ 1960 Larson 1063 07 2,953,4379/1960 Andrews 23209.9 2,960,413 11/1960 Voet 106307 3,005,725 10/1961Daniell 106307 3,011,902 12/1961 Jordan 106307 TOBIAS E. LEVOW, PrimaryExaminer.

ALEXANDER H. BRODMERKEL, Examiner.

J. B. EVANS, S. E. MOTT, Assistant Examiners.

1. IN A PROCESS FOR THE PRODUCTION OF CARBON BLACK PELLETS FOR USE ININKS WHICH COMPRISES AGITATING A FLOCCULENT COLOR GRADE CARBON BLACK INTHE PRESENCE OF A PELLETIZING MEDIUM CONSISTING OF OIL OR OIL/WATEREMULSIONS UNTIL SAID FLOCCULENT BLACK HAS BEEN SUBSTANTIALLY COMPLETELYCONVERTED INTO DISCRETE DUSTLESS PELLETS WHICH ARE SUITABLE FOR USE ININKS EXCEPT FOR AN UNDERSIRABLY ELEVATED LEVIGATION FACTOR THEIMPROVEMENT WHICH COMPRISES: DEPRESSING SAID LEVIGATION FACTOR TO ANACCEPTABLE LEVEL BY REMOVING FROM THE TOTAL MASS OF SAID PELLETSESSENTIALLY ONLY THOSE PELLETS HAVING DIAMETERS OF LESS THAN ABOUT 280MICRONS AND RECOVERING THE REMAINING PELLETS AS FINISHED PRODUCT.